Does anyone know how to force or change the image that Facebook grabs on shared threads? This mod works great for me but the Facebook post grabs my logo in the header which isn't a 1:1 ratio so it looks crappy on Facebook.

Go to the style you want to add it to. Open the conversation_toolbar template in that style and delete all code there. Then copy and paste the code in the attachment into the conversation_toolbar and save.
Don't forget to change the site name for your site.